This invention relates to a balloon catheter and, in particular to a process for mounting a polyurethane balloon on a polyethylene catheter.
Polyethylene is generally the preferred material for use in catheters because it will retain all of its desirable characteristics at body temperature and it is non-toxic. It is, however, difficult to bond most balloons to polyethylene. Certain processes have been developed by which latex balloons can be safely secured to polyethylene catheters. Latex, however, ages rapidly, particularly in the presence of light. Most cathers are packaged in clear plastic trays for sanitary and safety reasons, and as a consequence, those devices utilizing latex balloons have a very short shelf-life. Polyurethane balloons have been developed that overcome the storage problems associated with their latex counterparts. As described in U.S. Pat. No. 4,661,095, polyurethane ballons can be securely bonded to catheters formed of thermoplastic polyurethane using special polyurethane adhesives. Although polyurethane catheters work well in practice, they nevertheless do not provide all of the desirable characteristics demanded by many physicians.
One method of securing a balloon to a catheter is to tightly wrap the ends of the balloon with a fine thread or suture to provide a seal between the balloon and the catheter. This type of mechanical bond avoids many problems associated with adhesives, but usually requires that a metal ferule be placed under the windings to prevent the balloon from collapsing after inflation. These devices, therefore, are difficult to manufacture and generally increase the overall diameter of the catheter. A second method of bonding a balloon to a catheter is by stretching the ends of the balloon over the catheter and applying an adhesive to the junction between the balloon and the cather at both ends of the balloon. The adhesive is allowed to "wick" under the ends of the balloon by capillary action and thus sealing the joint. Typically, the adhesive will penetrate the joint to varying depths thereby resulting in uneven bonding. Control over the quality of the product is therefore difficult to maintain.